Intraspecific Wing Variation

A similar reduction in tegmina and wings often occurs in both sexes of a species. Sexual dimorphism is common, however, and it is most often the female that exhibits the greater degree of wing reduction. At one extreme are species with fully winged males and apterous females. Examples include the African genus Cyrtotria (= Agis) (Rehn, 1932a), Trichoblatta sericea, living on and under the bark of Acacia trees in India (Reuben, 1988), and many desert Polyphagidae. In A. investigata, for example, females are wingless, but at night fully winged males emerge from the sand and fly (Edney et al., 1974). Females of Escala circumductahave "almost discarded their organs of flight" and live their entire lives beneath the bark of trees. The fully winged males associate with the females only during a brief pairing season (Shaw, 1918). In cockroaches with extreme wing dimorphism females are often burrowers or crevice fauna, but the habitats of males are unknown, because they have been collected only at lights. Some cases of sexual dimorphism are so extreme that they are problematic to taxonomists trying to associate the two sexes (Roth, 1992). Females of Laxta (= Onisco-

soma) granicollis are flattened and wingless, resembling "an enormous wood louse," while males are winged and "of more graceful shape" (Swarbeck, 1946). Similarly, males of several species of Perisphaeria and Pseudoglo-meris are slender, winged insects, while the females are apterous and broader (Hanitsch, 1933). More moderate cases of wing dimorphism include species where both sexes have reduced wings but the female more so, and those species discussed above, where both sexes are fully winged, but the female is nonetheless flightless. We are not aware of cases of macropterous females and apterous males, but when wing reduction occurs in both sexes, sometimes the wings of the male are shorter (e.g., Para. stonei—Roth, 1990b).

Wing development within a species is not always a fixed character. In some cockroaches, only one sex exhibits variation, for example, Neotemnopteryx fulva males are macropterous, but the females may be macropterous or brachypterous (Roth, 1990b). Likewise, E. africanus males are macropterous, but female wing reduction varies with altitude (Rehn, 1932b). In other cockroaches, the reduction of tegmina and wings is variable in both sexes. These include at least five species of Panesthia (Roth, 1982b), H. concinnain the Galapagos (Roth, 1990a), and the Australian Para. couloniana (Roth, 1990b). The latter generally has brachypterous tegmina and mi-cropterous wings, but the degree of reduction varies, and there are males whose flight organs are fully developed. This species lives in litter and under bark, but there are also records of it infesting houses (Roach and Rentz, 1998).

Was this article helpful?

0 0

Post a comment